My car does the same. I've noticed it does it in D1/2 but never in 3. And it only does it in stop go traffic. For example when I'm in town and there are multiple red lights it starts in second. But on a service road where there are few red lights it starts in 1st. It also shifts to first no matter what on steep inclines. Because of how it works in these various situations I though it was normal so I never questioned it.